Abstract
Background:
Patients with recalcitrant anterior knee pain and isolated patellofemoral osteoarthritis (PFOA) may benefit from patellofemoral arthroplasty. Arthroplasty with an inlay implant may be beneficial given recreation of native biomechanics and potentially avoiding anterior overstuffing.
Indications:
Patellofemoral arthroplasty is indicated in patients with anterior knee pain from isolated PFOA in patients with neutral alignment and intact menisci and ligaments. To highlight these indications, we present a 32-year-old female with severe anterior knee pain from PFOA, not resolved by conservative measures. Preoperative imaging demonstrated full-thickness chondral loss of the lateral patellar facet and trochlea, with neutral alignment and no significant trochlear dysplasia.
Technique Description:
This technique utilized the HemiCap Wave Implant manufactured by Anika Therapeutics (Franklin, MA, USA). A standard midline approach and medial parapatellar arthrotomy is performed. The patella is everted, and the trochlea is exposed. A guide pin is placed perpendicular to the trochlear bony surface and centrally in the defect. The pin is advanced, and the surrounding area is reamed. A guide block is placed over the pin in the trochlea and over-reamed. The area is prepared and centrally drilled, then tapped. A taper post is implanted. The trochlear implant is then secured to the taper post with an impactor and mallet. On the patellar side, a guide pin is placed in the center of the patella. Consideration is given to medialization of the button to decrease Q-angle. The patella is reamed to the diameter of an appropriately sized patellar button. A trial button is used to ensure satisfactory tracking. A real patellar implant is then cemented into place. Standard closure is performed.
Results:
Overall outcomes following inlay patellofemoral arthroplasty have been positive, with up to 89% of patients engaging in sports at 2 years status post surgery and 83% survival free of total knee arthroplasty at 5 years postoperatively.
Discussion/Conclusion:
Patellofemoral arthroplasty can provide good satisfaction and high rates of return to sport in patients with symptomatic, isolated patellofemoral arthritis. The surgical technique video presented provides reproducible steps, tips, and tricks for performing this procedure.
This is a visual representation of the abstract.
Keywords
Video Transcript
The following is a video presentation for our preferred surgical technique for inlay patellofemoral arthroplasty (PFA).
We have no relevant disclosures.
In this video, we will discuss background information on patellofemoral arthritis and arthroplasty, provide our case presentation, follow this with our preferred surgical technique, discuss postoperative management, return to sport guidelines, and finish with published patient-reported outcomes.
Patellofemoral arthritis is common, with a published incidence of 25% to 39% in adult populations over 20 to 30 years of age. 3 Indications for PFA include isolated patellofemoral osteoarthritis (PFOA), the absence of concurrent tibiofemoral arthritis, and the absence of unaddressed patellar maltracking. 4 Considerations of inlay instrumentation include preservation of native geometry, as well as the fact that an inlay design is potentially advantageous in avoiding overstuffing.3,4
Our patient case revolves around a 32-year-old woman with chronic anterior knee pain due to PFOA. She rates her pain at level 6 to 10 out of 10 and rates her knee function as 20% of normal. She has tried extensive physical therapy as well as corticosteroid and hyaluronic acid injections, and a nerve block, without substantial, sustained benefit.
On physical examination, the patient had a body mass index (BMI) of 34, range of motion of 0 to 130°, which was symmetric bilaterally, and 5 minus out of 5 quadriceps strength due to anterior knee pain. In terms of her patellofemoral examination, the patient had 2+ retropatellar crepitus and a positive and painful patellar grind. She had no apprehension and satisfactory tracking with no J-sign. The patient had 2 quadrants of medial and lateral patellar glide with a firm endpoint. Her knee was otherwise stable in all planes.
Standard knee radiographs were obtained and demonstrated maintenance of the medial and lateral tibiofemoral joint spaces on her weightbearing posterior-to-anterior (PA), as well as lateral views. A merchant view demonstrated patellofemoral osteophytes but preservation of the medial facet joint space and early lateral wear. Given radiographs which were indicative of patellofemoral disease, we proceeded with a magnetic resonance imaging (MRI) to further characterize her patellofemoral changes.
Axial views demonstrated essentially full-thickness chondral loss of the lateral facet with associated bipolar loss of the lateral aspect of the trochlea. There is a substantial effusion, and there is also subchondral edema noted in the patella. The patient’s tibial tubercle-trochlear groove (TT-TG) distance fell within normal limits at 13 millimeters, and her trochlea demonstrated mild, Dejour A dysplasia. Her medial and lateral joint spaces were well preserved. Given refractory pain from bipolar patellofemoral chondral disease and satisfactory patellar alignment, the decision was made to proceed with an inlay PFA with the HemiCap Wave Implant manufactured by Anika Therapeutics (Franklin, MA, USA).
The patient was positioned supine and prepped and draped in a standard surgical fashion. An approximately 12-cm incision was made over the anterior aspect of the knee, extending from 2 cm proximal to 3 cm distal, along the axis of the patella. Full-thickness medial and lateral skin flaps were then raised. We then marked out a medial parapatellar arthrotomy with cautery and used a sharp, fresh blade to create a medial parapatellar arthrotomy, ensuring that the underlying cartilage and meniscus are protected.
The patella is everted and held in place laterally using a Z-retractor. A Z-retractor is placed medially, and an army-navy (retractor) is placed proximally. A sizing template is then used to measure the medial-to-lateral offset, as well as the superior-to-inferior offset of the trochlea.
An offset drill guide is then placed perpendicular to the central trochlear articular surface to create a working axis for instrumentation. A 2.5-mm guide pin is advanced to the level of the marking at the back of the guide. An appropriately sized central reamer is then advanced over the guide pin and reamed until the etched sides of the reamer are flush with the medial and lateral articular cartilage.
Reamings are cleared from the surgical field, and a guide block (corresponding to the previously measured superior to inferior offset) is centered in the trochlear groove. The guide block is gently malleted into place, such that it is flush with the articular surface and then secured with up to four 2.5-mm guide pins.
The outer reamer is placed into the guide bushing and secured into the superior aperture of the guide block. Subsequently, the outer reamer is used to ream to the level of the depth mark on the reamer shaft. This process is then repeated with the cutter, advancing it until the guide mark is reached.
This process is then repeated in the inferior aperture of the guide block, first using the outer reamer, then using the cutter. After completion, the guide block pins and guide block are removed. The field is pulse-lavaged of any debris, and a rongeur and curette are used to clear the prepared bed.
A trial handle is placed on an appropriately sized trial and is gently malleted into the prepared site. This is held into place with two 2.5-mm pins. The pilot drill is introduced through the center of the trial handle, and drilling is performed to the level of the laser mark on the cannulated pilot drill. The pilot drill is left in place and the trial handle is removed.
Subsequently, the step drill is advanced over the pilot drill, reaching a positive stop. The step drill is removed, and a tap is advanced over the step drill until it is flush to the back of the pilot drill. Both the pilot drill and the tap are then removed.
A taper post is opened and placed onto the Morse taper of the trial handle. This is then secured into place by turning the hex driver until a positive stop is reached on the trial handle. Once placed at proper depth, the sizing trial and associated pins are removed. The prepared bony area is cleaned in anticipation of trochlear component placement.
An appropriately sized trochlear component is opened and placed onto the prepared bed, aligned with the previously implanted taper post. This is firmly malleted into place with a curved impactor until seated evenly with the articular surface.
Attention is then turned to patellar preparation. The patella is everted with the knee in extension, and an appropriately sized patellar component is selected based on native anatomy. A 2.5-mm guide pin is inserted through the selected patellar sizing trial, perpendicular to the patella. Leaving the guide pin in place, a patellar reamer is then used over the guide pin to prepare the patella to the level of the markings on the side of the reamer. The reamer and central pin are removed.
To enhance fixation, we then use a 2.5-mm pin or K-wire to create 6 to 8 additional areas of cement fixation and interdigitation in the prepared bed. A trial component is placed. The knee is cycled through range of motion, prior to cementation to ensure satisfactory tracking.
Finally, low viscosity cement is applied to the back of the real patellar component. The component is placed in the prepared bed and clamped firmly in place with the patellar clamp, ensuring that the back end of the clamp is away from the overlying skin. Prominent osteophytes or cartilaginous flaps are debrided. The cement is allowed to harden. Once all cement is dried, the clamp is removed. Any excess cement is removed. The knee is then closed in layers in a standard fashion.
General complications of PFA are similar to that of general knee surgery. This includes infection, which has been published at rates of 0 to 6%, and deep venous thrombosis, which can follow any lower extremity surgery.2,3,4 The most common reason for PFA failure is the progression of osteoarthritis of other knee compartments.2,3 Less common reasons are aseptic loosening, for which we recommend meticulous cementation technique, and maltracking. 3
In terms of tips and tricks, careful patient selection is key to success in PFA. This procedure should ideally be performed in patients with symptoms of isolated, recalcitrant patellofemoral arthritis, refractory to nonoperative management.
If performed in the setting of patellar instability, surgeons should measure tibial tubercle to trochlear groove distance, as well as obtain a preoperative alignment view to evaluate for pathologic valgus. Consideration should be given to the addition of concurrent medial patellofemoral ligament reconstruction in patients with a clinical history of dislocation, excessive lateral patellar translation, and apprehension on preoperative examination.
Similarly, consideration can be given to tibial tubercle osteotomy for patients with bony malalignment, which is the result of a pathologically increased TT-TG, often >20 mm. In addition, one can consider shifting the patellar button medially to decrease the Q-angle and improve tracking.
Patients with severe, Dejour B or D dysplasia should prompt consideration of larger design implants, such as the Anika Kahuna, to address their broad and shallow trochlear pathomorphology. Surgeons should also ensure a smooth proximal transition from native anatomy to implant, which may merit resection or smoothing of a supratrochlear bump.
Finally, in older patients with isolated PFOA undergoing PFA, consideration should be given to cement-based fixation augmentation at the trochlear bone-implant interface.
In terms of postoperative treatment and rehabilitation, patients are begun with immediate weightbearing, as tolerated, and full range of motion starting postoperative day 0. At 2 weeks postoperatively, we see our patients again in a clinic visit to perform a wound check and ensure that their wound is satisfactorily healing. If this is the case, then the patients begin physical therapy. At 16 weeks postoperatively, we obtain radiographs to ensure that the implant remains appropriately fixed and in good position, and consideration is given to return to sport. Return to sport is done as tolerated, and generally occurs at 16 weeks postoperatively, when patients have satisfactory range of motion as well as strength.
Overall outcomes following inlay PFA have been positive. In terms of return to sport, Imhoff et al, in their 2-year outcomes study, reported that 58% of patients were engaged in sport prior to PFA, and 89% of patients were able to engage in sports at the time of final follow-up. 2
Similarly, in another study by Imhoff et al, 263 PFAs were evaluated at a minimum of 2 years postoperatively. 1 Patient satisfaction rate was 93%. Patients reported significant postoperative improvements in Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) outcome scores. At final follow-up, 11% of patients had converted to arthroplasty. Of note, 82% of failures had no prior patellar resurfacing at that time of their index inlay trochlear arthroplasty, highlighting the utility of patellar resurfacing in this patient population.
In conclusion, inlay PFA demonstrates satisfactory outcomes in patients with isolated patellofemoral arthritis. In addition, the majority of patients participating in preoperative sports can return to their previous level of function. Finally, the presented technique is reproducible with use of readily implemented drill, reamer, and sizing guides.
The following are our references.
We thank you for your time and attention.
Footnotes
Submitted February 23, 2022; accepted April 21, 2022.
One or more of the authors has declared the following potential conflict of interest or source of funding. M.H. is a paid consultant for Moximed. E.J.B. received stock or stock options from Amgen, Co. and Pfizer. B.F. received grants or contracts from Arthrex, Inc, Smith & Nephew, and Stryker; received royalties or licenses from Elsevier; received consulting fees from Smith & Nephew; received stock or stock options from I-BrainTech, Jace Medical, and Sparta Biopharma; and has a leadership or fiduciary role in other board, society, committee or advocacy group, paid or unpaid, for American Orthopaedic Society for Sports Medicine (AOSSM) and the Video Journal of Sports Medicine. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
